This application is submitted in response RFA-CA-11-011 Research Answers to NCI's Provocative Questions (R01) and specifically focuses on addressing PQ-1: How does obesity contribute to cancer risk? This application builds upon the large collection of biospecimens including germline DNA, normal and tumor tissues, and comprehensive epidemiology data including diet, obesity, and physical activity of an ongoing renal cell carcinoma (RCC) case control study from Texas. Currently, we have accrued 1,270 patients with newly diagnosed RCC of Texas residence from MD Anderson Cancer Center and 1,200 matched controls identified from random digit dialing of Texas residents. By the time the grant is funded, we estimate to recruit at least 50 cases and 50 controls. We plan to recruit an additional 350 patients and 350 controls. The application will investigate the role of obesity and energy balance in modulating RCC risk as a step towards a clear understanding of the factors that contribute jointly to obesity and cancer development. We will test the hypothesis that obesity-related genetic variations, mtDNA alterations, and epigenetic status (microRNA and methylation) drive RCC tumorigenesis, and interactions among these factors with obesity and energy balance (dietary intake and physical activity) can further modulate risk. Towards this, we will explore 4 specific aims: 1) To identify novel germline susceptibility loci for RCC risk focusig on obesity-related loci and variation in methylation and miRNA pathways. We will use two-stage design to first screen ~ 10,000 previously identified obesity-related loci and potential functional and haplotype-tagging SNPs in epigenetic pathway genes in 800 cases and 800 controls and then validate top 500 SNPs in additional 800 cases and 800 controls; 2) To determine the effect of mtDNA alterations (copy number and genetic variations) on RCC risk and evaluate the joint effect of mtDNA alterations, obesity, diet, physical activity, and genetic variation identified in im 1 in modulating RCC risk. We will measure mtDNA copy number and genotype all the 144 mitochondrial SNPs with a minor allele frequency >1% in 1,600 cases and 1,600 controls; 3) To identify CpG island methylation of obesity-related genes and miRNA expression patterns in 400 paired RCC tumors and adjacent normal tissues and global methylation status in 1,600 cases and 1,600 controls and 400 paired RCC tumors and adjacent normal tissues; We will determine the interplay between of obesity and energy balance on these phenotypes; 4) To assess genotype-phenotype correlations in obesity-related pathways and mtDNA content and epigenetic events. By integrating epidemiological data, germline genetic variations associated with obesity and epigenetic alterations, mitochondrial function, and profiling of epigenetic alterations in tumors, this comprehensive project will not only shed significant light into the etiology and pathogenesis of RCC, but also identify the commonality of these molecular pathways in obesity and cancer development.